> persistence can be better achieved by clustering

If you want persistence, then I'd recommend persisting to disk. While I've not had this fun with Redis, I've written code that took out an entire Cassandra ring. Were stuff only in memory, it would have not been pretty. Just because something is distributed doesn't mean it's guaranteed to never go completely down.

(That said, if you're using Redis as an in-memory cache, this is a potentially acceptable tradeoff.)